1. Field of The Invention
The present invention relates to a curable polyphenylene ether resin composition, a cured polyphenylene ether resin composition and a laminate structure. More particularly, the present invention is concerned with a curable polyphenylene ether resin composition comprising a reaction product obtained by reacting a polyphenylene ether with an unsaturated carboxylic acid or an acid anhydride, and at least one cyanurate. Also, it is concerned with a resin composition containing an epoxy resin or a reinforcement material if necessary, and a cured material thereof. Further, it is concerned with a laminate structure comprising a metallic foil and at least one cured resin composition layer disposed on at least one surface of said metallic foil.
The curable polyphenylene ether resin composition of the present invention has excellent storage stability, film forming properties and melt moldability, and the cured polyphenylene ether resin composition of the present invention has excellent chemical resistance, electrical properties (such as low dielectric constant and low dielectric dissipation factor), fire retardance, dimensional stability and heat resistance. Accordingly, the cured polyphenylene ether resin composition can advantageously be used as a dielectric material, an insulating material, a heat resistant material and the like in, for example, electrical and electronic industries, space and aircraft industries, etc.
The laminate structure of the present invention can advantageously be used as a single-sided printed circuit board, a double-sided printed circuit board, a multi-layer printed circuit board, a flexible printed circuit board and the like.
2. Discussion of Related Art
In recent years, miniaturization and high-packing-density mounting have been strongly desired in the field of electronic devices for communication, household, industries and the like. Accordingly, materials for such devices having excellent heat resistance, dimensional stability and electrical properties have been strongly desired in the art. For example, a copper-clad laminate made Of a substrate comprising a thermosetting resin, such as a phenol resin and an epoxy resin, has been used as a printed circuit board. However, such a thermosetting resin has a drawback in that the resin has undesirable electrical properties, particularly an undesirably high dielectric constant in a high frequency range, although the resin has a good balance of various properties.
For overcoming the above-mentioned drawback, polyphenylene ether has been attracting attention as a new material, and it has been attempted to apply a polyphenylene ether to a copper-clad laminate. Indeed, a polyphenylene ether is one of the typical engineering plastics which has not only excellent mechanical but also desired electrical properties, such as a low dielectric constant and a low dielectric dissipation factor, and has also a relatively good heat resistance. However, when a polyphenylene ether is used as a material for a printed circuit board substrate, the heat resistance thereof is insufficient. A material for a printed circuit board substrate is required to have an extremely high heat resistance, because a printed circuit board substrate is necessarily exposed to high temperatures in soldering. However, substrates made of conventional polyphenylene ethers are likely to undergo distortion at temperatures higher than about 200.degree. C., thereby causing a considerable decrease in mechanical properties and peeling off of copper foils provided as circuits on the surface of the substrate. A polyphenylene ether has also another drawback in that it has such poor resistance to an aromatic hydrocarbon and a hydrocarbon substituted with a halogen atom that it is ultimately dissolved in such hydrocarbons, although the polyphenylene ether has excellent resistance to acids, alkalis and hot water.
For improving the heat resistance and chemical resistance of a polyphenylene ether, various proposals have been made, in which a polyphenylene ether is formulated into a composition. For example, Japanese Patent Application Laid-Open No. 287739/1986 discloses a composite structure comprising as a resin substrate a cured resin obtained by curing a resin composition comprising a polyphenylene ether and at least one member selected from the group consisting of triallyl cyanurate and triallyl isocyanurate. The cured resin has poor chemical resistance, e.g., poor resistance to boiling trichloroethylene, and poor fire retardance, so that the composite structure is not suited for use as a printed circuit board. In a method comprising preparing a solution of the resin composition and fabricating the solution into a film according to a casting method, the resin composition solution has poor film-forming properties, so that disadvantageously it is difficult to obtain a film with a smooth surface.
On the other hand, with respect to general-purpose printed circuit boards comprising a glass fiber-reinforced epoxy resin substrate, various proposals have also been made to improve the heat resistance and electrical properties thereof. For example, it was proposed to improve the heat resistance and electrical properties of such printed circuit boards by employing a resin blend comprising a polyphenylene ether and an epoxy resin. In this connection, reference is made to Japanese Patent Application Laid-Open No. 69052/1983 and Japanese Patent Application Publication No. 3223/1989, in which a composite structure comprising a resin layer comprised of a polyphenylene ether and an epoxy resin and a glass fabric is disclosed. The chemical resistance of the resin layer of the composite structure is not satisfactory, and hence the composite structure is not suitable for use as a printed circuit board.
Japanese Patent Publication No. 3223/1989 and European Patent Publication Examined No. 315829 disclose combinations of a polyphenylene ether with various types of epoxy resins. As the epoxy resins, general epoxy resins such as a polyglycidyl ether of bisphenol A, an epoxy phenol novolak resin and the like are used. Curing of these compositions is achieved by using various publicly known curing agents including amines. However, a polyphenylene ether used in the invention is not chemically modified. Therefore, the cured compositions are remarkably deficient in resistance to boiling trichloroethylene, which is required as a material for a printed circuit board since the cured compositions do not have chemical resistance at all.
U.S. Pat. No. 4,912,172 discloses a resin composition comprising (i) a polyphenylene ether, (ii) a bisphenol polyglycidyl ether, and (iii) aluminum or a zinc salt as a material to improve chemical resistance. Further, European Patent Publication unexamined No. 0 350 696, Japanese Patent Application Laid-Open No. 55722/1990, and U.S. Pat. No. 5,043,367 disclose a resin composition comprising (i) a polyphenylene ether, (ii) an epoxy resin composition containing bromine, (iii) a novolak resin, (iv) an imidazole and a polyamine, (v) a zinc salt, and (vi) Sb.sub.2 O.sub.5 as a material to give flame retardance.
European Patent Publication unexamined No. 383 178 discloses a resin composition comprising (i) a polyphenylene ether having a low molecular weight, (ii) an epoxy resin composition containing bromine, (iii) an imidazole and a polyamine, and (iv) aluminum or a zinc salt as a material to improve resin flow properties.
As a material which undergoes modification of a polyphenylene ether itself, Japanese Patent Application Laid-Open No. 135216/1990 discloses a resin composition comprising (i) a reaction product of a polyphenylene ether with an unsaturated carboxylic acid or an acid anhydride, (ii) a polyepoxy compound, and (iii) an epoxy cure catalyst, and U.S. Pat. No. 5,001,010 discloses a resin composition comprising (i) a melt processed polyphenylene ether, (ii) a polyepoxy compound, and (iii) an epoxy cure catalyst.
However, these compositions proposed in the above-mentioned patents and patent applications do not show sufficient improvement in resistance to trichloroethylene so that remarkable changes of appearance such as surface roughness and the like in the cured resin compositions are observed when these cured resin compositions are tested in a boiling trichloroethylene.